'The end of the human race'. On the list of doomsday scenarios that could wipe out the human race, super-smart killer robots rate pretty high in the public consciousness.
All stars live by fusing hydrogen into helium. In the first step of the process, two hydrogen atoms fuse to form deuterium. In the next step, another hydrogen atom fuses with the deuterium, creating a rare isotope of helium that has two protons and one neutron in its nucleus. In the third step, two of the rare helium atoms fuse to create a single normal helium atom and two hydrogen atoms. The fusion pathway described above requires six hydrogen atoms to create one helium atomâhowever, there are two hydrogen atoms left over at the end of the process. The net result is that it takes four hydrogen atoms to make one helium atom.
That is to say if a protostar has at least 0.08 times the mass of our sun and has a temperature of at least 107 K, hydrogen fusion can begin in it and it will become a star. Hydrogen fusion is the longest stage in an active stars life and so is considered the main sequence of a star.1]. The other process through which hydrogen can fuse into helium in a star is called the carbon cycle. This process will occur if the star has carbon present with in it and if the stars temperature is 2x107 K or greater. Equations (6)-(11) outline the series of reactions that occur in the carbon cycle.